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    <title>Document</title>
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    <script>
      function Star(uname, age) {
        this.uname = uname
        this.age = age
      }
      var that
      Star.prototype.sing = function () {
        console.log("我会唱歌")
        that = this
      }
      var shiyuan = new Star("石原里美", 18)
      // 1. 在构造函数中，里面this指向的是对象实例
      shiyuan.sing()
      // 2.原型对象函数里面的 this 指向的是实例对象
      console.log(that === shiyuan)
    </script>
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